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 *   Copyright (c) 2022 Huawei Device Co., Ltd.
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abstract class CharDistributionAnalysis {
  ////////////////////////////////////////////////////////////////
  // constants
  ////////////////////////////////////////////////////////////////
  public static  SURE_NO:number = 0.01;
  public static  SURE_YES:number = 0.99;
  public static  ENOUGH_DATA_THRESHOLD:number = 1024;
  public static  MINIMUM_DATA_THRESHOLD:number = 4;

  ////////////////////////////////////////////////////////////////
  // fields
  ////////////////////////////////////////////////////////////////
  private freqChars:number;
  private totalChars:number;
  protected charToFreqOrder:number[]; // set by subclasses
  protected typicalDistributionRatio:number; // set by subclasses

  ////////////////////////////////////////////////////////////////
  // methods
  ////////////////////////////////////////////////////////////////
  public constructor() {
    this.reset();
  }

  public  handleData(buf:ArrayBuffer, offset:number, length:number):void {
  }

  public  handleOneChar(buf:ArrayBuffer, offset:number, charLength:number):void {
    let order:number = -1;
    if (charLength == 2) {
      order =this.getOrder(buf, offset);
    }
    if (order >= 0){
      ++this.totalChars;
      if (order < this.charToFreqOrder.length) {
         if (512 > this.charToFreqOrder[order]) {
            ++this.freqChars;
         }
      }
    }
  }

  public getConfidence():number {
    if (this.totalChars <= 0 || this.freqChars <= CharDistributionAnalysis.MINIMUM_DATA_THRESHOLD) {
      return CharDistributionAnalysis.SURE_NO;
    }
    if (this.totalChars != this.freqChars) {
      let r:number = this.freqChars / ((this.totalChars - this.freqChars) * this.typicalDistributionRatio);
      if (r < CharDistributionAnalysis.SURE_YES) {
        return r;
      }
    }
    return CharDistributionAnalysis.SURE_YES;
  }

  public reset():void {
    this.totalChars = 0;
    this.freqChars = 0;
  }

  public  setOption():void {
  }

  public  gotEnoughData():boolean {
    return (this.totalChars > CharDistributionAnalysis.ENOUGH_DATA_THRESHOLD);
  }

  protected abstract getOrder(buf:ArrayBuffer, offset:number):number;
}

export default CharDistributionAnalysis